Adding language packs to Windows XP Pro?

I want you to know I used Google before posting, but I could only find stuff about changing the language of Windows, which I don't want to do. The search function of the forum didn't give me an answer either.

If you look at the Kanji titel of this anime , for me, it's just ••••. But on my laptop, I see it as actual Kanji.

How can I add language packs to Windows so I can see the language? I know it's possible in the installer of Windows, but how do I add them afterwards?

I didn't install my laptop, it came pre-installed because I only use it for school. So I don't know how the language pack got on it.